Max Planck Institute for Astronomy

Astronomy is one of the oldest sciences – and yet also one of the most modern. The Max Planck Institute for Astronomy in Heidelberg is proof of this. The researchers here decipher the mysteries of the universe with high-tech instruments, constructing clever add-ons and detectors for telescopes and satellites which examine the light from cosmic sources according to all the laws of physics. Infant stars and the birth of planetary systems are but two objects of their scientific curiosity. “Is Earth the only inhabited place in the universe?” is one of their burning research questions. The Max Planck astronomers also travel through the depths of space and time, investigating active galaxies and quasars to gain an idea of the beginning and the development of today’s richly structured universe.

The yearbook of the Max Planck Society illustrates the research carried out at our institutes. We selected a few reports from our 2017 yearbook to illustrate the variety and diversity of topics and projects.
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He loves basketball and literature, but his real passion is cosmology. Joe Hennawi uses telescopes and supercomputers to investigate the largest structures in the universe at the Max Planck Institute for Astronomy in Heidelberg – in a research group called ENIGMA. Their aim is nothing less than to unravel the mysteries of the cosmic web.

The universe has billions and billions of galaxies, but only one that we can explore star by star in all its dimensions: our Milky Way. It can be thought of as a “model organism” for the formation and evolution of galaxies and is thus a key research topic in cosmology, and the research focus of the team working with Hans-Walter Rix, Director at the Max Planck Institute for Astronomy in Heidelberg. The researchers recently found indications that quite a number of earlier ideas about our galaxy have to be revised.

Magnetic fields spanning 100,000 light-years permeate entire galaxies and envelop their central black holes. Researchers working together with Rainer Beck, Silke Britzen and Sui Ann Mao at the Max Planck Institute for Radio Astronomy in Bonn are teasing the secrets out of these invisible force fields.

They are often eclipsed by more attractive topics, like black holes or exoplanets. Even the name itself is less than sensational: brown dwarfs. But Viki Joergens and her colleagues from the Max Planck Institute for Astronomy in Heidelberg have gained fascinating insights in this research field.

When the universe came into being 13.7 billion years ago, there was initially onlyradiation. A few hundred million years later, however, the space was filled with galaxies –tremendously productive star factories that don’t fit quite so well with the image of agradual cosmic evolution. Researchers like Fabian Walter from the Max Planck Institutefor Astronomy in Heidelberg are attempting to illuminate a dark epoch of the universe.

To date, astronomers have discovered nearly 800 planets orbiting distant stars. So far, only three of them have been found to potentially offer life-sustaining conditions. However, there are probably many second Earths in the Milky Way. But how can traces of life be detected on exoplanets? At the Max Planck Institute for Astronomy in Heidelberg, Lisa Kaltenegger is trying to answer this question.

Exoplanets – planets that orbit stars other than the Sun – used to be a matter of science fiction. Some 15 years ago, with the first detection of an exoplanet, they became a matter of observational astronomy. Since then, exoplanet observations have provided astronomers with intriguing clues as to the formation of stars and planets.

Astronomers from McMaster University and the Max Planck Institute for Astronomy have completed calculations that lead to a consistent scenario for the emergence of life on Earth, based on astronomical, geological, chemical and biological models. In this scenario, life forms a mere few hundred million years after Earth’s surface was cool enough for liquid water; the essential building blocks for life were formed in space during the formation of the solar system, and delivered to warm little ponds on Earth by meteorites.
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Astronomers believe that matter in intergalactic space is distributed in a vast network of interconnected filamentary structures – the cosmic web. Nearly all the atoms in the Universe reside in this web, left over from the Big Bang. A team led by a team of the MPI for Astronomy has made the first measurements of small-scale fluctuations in the cosmic web just 2 billion years after the Big Bang. These measurements were enabled by a novel technique using pairs of quasars to probe the cosmic web along adjacent lines of sight. They promise to help astronomers reconstruct the epoch of reionization.
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Two astronomers have produced the first direct images of a gigantic X-shaped distribution of stars in the center of the Milky Way. The collaboration began when Dustin Lang (University of Toronto) tweeted an image he had recently created. From the tweet, Melissa Ness (MPIA) recognized the image's significance for reconstructing the history of our home galaxy. The X-shaped distribution indicates that the bulge of stars surrounding the center of the galactic disk was formed through dynamical interactions of stars, not by the merger of smaller galaxies with our own.
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Astronomers have discovered a planet orbiting the nearest star outside our solar system, Proxima Centauri. The planet, designated Proxima Centauri b, is in the habitable zone of its star, where liquid water could exist. The discovery is the result of a patient search using the radial velocity method, which searches for tiny wobbles of a star caused by an orbiting planet. In addition to newly acquired data, the analysis uses spectra taken by MPIA astronomer Martin Kürster and colleagues between 2000 and 2007.
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Astronomers have presented the first detailed study of the atmospheric features – the extraterrestrial wea ther patterns – of a brown dwarf (an intermediate object between planet and star). The results include the first surface map of a brown dwarf and measurements at different wavelengths probing its atmosphere at different depths. They mark the beginning of an era in which astronomers will be able to compare models for cloud formation on brown dwarfs – and, eventually, on giant gas planets in distant star systems – with observations.
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A team led by astronomers from the MPI for Astronomy has created the first three-dimensional map of the "adolescent" Universe, just 3 billion years after the Big Bang. Applying a new technique analogous to x-ray computer-tomographic (CT) imaging, the researchers measured the light from a dense grid of distant background galaxies probing the Universe from multiple locations, and then constructed a 3D map of the intervening matter. This map, millions of light years across, provides a tantalizing glimpse of large structures in the "cosmic web", which forms the backbone of cosmic structure.
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A combination of the Herschel Space Observatory with the submillimeter telescope APEX leads to the discovery and characterization of the youngest known protostars yet: stellar embryos still deeply embedded in unexpectedly dense dust cocoons.
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Pinpointing the positions of more than 100 of the most fertile star-forming galaxies with the compound telescope ALMA clears up a mystery about these objects' observed productivity – and shows that previous studies had frequently mis-identified such galaxies.
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An infrared imaging search with the Subaru telescope has captured a rare image of a “Super-Jupiter” around the massive star κ Andromedae. The gas giant has a mass about 13 times that of Jupiter, while the host star has a mass 2.5 times that of the Sun. There are strong indications that this planet formed in a manner similar to ordinary, lower-mass exoplanets: in a “protoplanetary disk” of gas and dust that surrounded the newborn star. This makes the planet an important test case for current models of planet formation and their predictions about planets around massive stars.
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A group of astronomers led by Remco van den Bosch from the Max Planck Institute for Astronomy has discovered a black hole that could shake the foundations of current models of galaxy evolution. At 17 billion times the mass of the Sun, its mass is much greater than current models predict – in particular in relation to the mass of its host galaxy. This could be the most massive black hole found to date.more

Astronomers at the Max Planck Institute for Astronomy have measured for the first time the alignment of magnetic fields in gigantic clouds of gas and dust in a distant galaxy. The results suggest that such magnetic fields play a key role in channelling matter to form denser clouds, and thus in setting the stage for the birth of new stars. The work was published in the November 24 edition 2011 of the journal Nature.
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Using state-of-the-art technology and sophisticated data analysis tools, a team from MPIA has developed a new and powerful technique to directly determine the mass of a galaxy hosting an active supermassive central black hole at a distance of nearly 9 billion light-years from Earth. This pioneering method promises a new approach for studying the co-evolution of galaxies and their central black holes, which typically relies on mass determinations.
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Measurements were made of the velocities of a large number of stars in a young galactic cluster, whose age is only about one million years. The cluster is embedded in the bright emission nebula NGC 3603. It is one of the most massive objects of its kind within the Milky Way. To determine the individual stellar velocities, the astronomers compared the positions of the stars on two images taken with the Hubble Space Telescope ten years apart. From this comparison the motion of hundreds of stars could be determined, showing that the cluster stars have not yet reached a dynamically configuration.
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Spiral galaxies grow by swallowing smaller dwarf galaxies. As they are digested, these dwarf galaxies are severely distorted, forming structures such as surreal tendrils and stellar streams that surround their captors. Now, for the first time, a new survey has detected such tell-tale structures in galaxies more distant than our immediate galactic neighbourhood. This opens up the possibility of testing our current views of galaxy evolution in a new way.
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The very first observations with HiCIao, the world’s newest instrument in the search for extrasolar planets, have led to the discovery of G 758 B, the low-brightness companion of the star GJ 758. This is possibly the first direct observation of a cool extrasolar planet orbiting a Sun-like star. The mass of GJ 758 B is estimated to be between 10 and 40 Jupiter masses. The temperature of GJ 758 B – 600 Kelvin (330 degrees Celsius) – makes it the coldest companion of a Sun-like star ever to be imaged directly, and thus the companion most similar to the planets of the solar system.
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When large galaxies come close to one another, the resulting tidal forces initiate intense star-forming activity. However, this process does not play a very important role in the formation of stars in general. In fact, an international study headed by the Max Planck Institute for Astronomy has shown that the formation of no more than ten percent of all new stars has been initiated directly by gravitational interaction in mass-rich galaxies during the last eight billion years (at redshifts z < 1). This finding is of great significance for the theory of galaxy evolution.
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Several hundred Brown Dwarfs have been identified in the solar neighborhood and seem to be as numerous as main sequence stars. But the models for their structure and evolution are not as reliable as the models for stars. Spatially resolved binary systems offer a unique opportunity to determine the masses without using models, but such cases are rare. A group at the MPIA has now succeeded in determining the parameters of the Brown Dwarfs Kelu-1A and B. Conclusion: Existing models yield masses which are too low. The spectra also suggest the presence of an invisible third Brown Dwarf in Kelu-1.
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A group of astronomers headed by the Max Planck Institute for Astronomy has measured the velocity of the stars in the galactic halo and thereby derived the most accurate value to date for the total mass of the galaxy: The region within a radius of 200 000 light years contains 4×1011 solar masses. An extrapolation to 800 000 light years leads to 1012 solar masses. This result shows that the mass of the Milky Way has previously been significantly over-estimated. It also proves that our Milky Way has been extraordinarily efficient at forming stars.
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The discovery of the first planet around another star than the Sun in 1995 gave this field of astronomical research an enormous observational and theoretical impetus. At the Max Planck Institute for Astronomy (MPIA) the search for exoplanets and the numerical simulation of the formation of planets is an important area of research. Within a long-term survey, a team at the Institute has now found the youngest planet known so far in the circumstellar disk of the eight to ten million years old star TW Hydrae. The discovery has important implications regarding the formation of planets in the circumstellar disks around newborn stars.
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With the decisive participation of the Max Planck Institute for Astronomy (MPIA), on Mount Graham in Arizona the Large Binocular Telescope is being erected. It consists of two primary 8 meter mirrors supported by a common mounting. In spring of 2007, first observations were performed with one of the two mirrors. The first results were published in a study by MPIA’s Matthew Coleman and his colleagues, which refers to three dwarf satellite galaxies accompying the Milky Way system: their peculiar morphologies result from the complex history of their evolution due to strong gravitational interaction with the Milky Way.
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Massive stars are much rarer and they form much faster than low-mass stars – which is why it is quite unlikely to be able to observe their early stages. In addition, all regions with massive young stars are at a greater distance from our solar system, resulting in stringent requirements for the resolution and sensitivity of the instruments used for observation. However, today the new interferometers in the sub-millimeter and millimeter range enable the investigation of more distant star formation regions at high spatial resolution and sufficient sensitivity. An international team lead by MPIA managed to gain interesting insights into several massive star-forming regions, including the famous Orion KL region.
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Cassiopeia A is the youngest known supernova remnant in our Galaxy. Although unrecorded at the time, it must have exploded around 1680. The nebula, lying at a distance of about 11000 light years, is one of the best-studied celestial objects. Astronomers succeeded in detecting light echoes in the infrared range around the supernova remnant. These originate from interstellar dust that was heated by the flash of the supernova explosion and by flares of the central neutron star.
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During close encounters or collisions of galaxies huge tidal forces occur that whirl up and compress the dust and gas in the galaxies. This induces a steep increase of star formation. With the help of computer simulations, it was shown how the star formation rate, dust absorption, and observed appearance of the galaxy change during a merger and an analytical formula was derived which can be used to predict the dust absorption.
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Very massive stars terminate their short but intensive life with a powerful explosion - a Supernova. The energies set free are enormous making such explosions bright enough that they may outshine a whole galaxy for a short time. An expanding shell of dust and gas surrounding a neutron star remains, one could call the skeleton of the exploded star. A team of astronomers at the Max Planck Institute for Astronomy in Heidelberg and in the USA has found evidence, with the help of the space telescope SPITZER, that the exploded star responsible for the Supernova Cassiopeia A is still extremely active even 325 years after its death.
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In 2003, large quantities of dust were detected in the most distant quasars. So the question arose how this dust could possibly have formed within only about 700 million years after the big bang. The mystery soon seemed to be solved: a team of astronomers claimed to have detected enormous amounts of dust in the Cassiopeia A (Cas A) supernova remnant. The scientists concluded from this that type II supernovae were the first to produce dust in the universe. When astronomers at MPIA followed up this issue they came to a different conclusion: The dust detected at Cas A has nothing to do with the supernova remnant but actually belongs to an extended dust complex lying between Earth and Cas A. Thus the question about the origin of the dust in the early universe is still open.
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After the first successful tests of the mid-infrared interferometric instrument MIDI at the ESO Very Large Telescope at the end of 2002, the phase of Science Demonstration followed in the year under report. MIDI fully met the high expectations and thus opened up a new field of astronomical observations: for the first time a resolution of one hundredth of an arc second can be achieved in the mid-infrared spectral range. Observations of circumstellar disks around young stars as well as of the dust ring in the center of an active galaxy demonstrate the enormous power of the instrument. MIDI was built by a consortium of German, Dutch, and French teams under the leadership of MPIA.
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